Just today we've had 5 frames, 2 from Cal and 3 that Kassandra caught while checking frames, where the threads will pull out of the top of the extrusion(HD-EX0062). Its always the top M5x10 that goes through the Z upper and into the top of the extrusion. Its really costly when the machine has made it to Cal and has to be reworked, but is still very much a pain to replace when its just a frame.
@tutley This could also be related to an issue were seeing with the extrusions look like they were drilled to large and then tapped with M5 threads. One think we need to do is perhaps have the frame assemblers be a bit more vigilant about what t-slot extrusions they are using.
@wolffchadd Tagging wolf in this ticket as well.
Kent will be in the building tomorrow and I will have him look at them. If we need to communicate to the vendor we will need the amount that are non conforming to send back and get a credit on.
The other day I had them stripping out when tightening them by hand, without putting a tool on them. It almost seems like only a couple threads on the screws are all that holds the extrusion the the uppers.
While I believe it is true that the extrusions are non-conforming having seen one myself this morning, we could stand to have better thread engagement on the top plate. The amount of thread engagement is reduced vs TAZ 6 because of the thicker top plate.
We could use HD-BT0158 M5x12 BHCS on top, and depending on what percentage becomes fallout, and whether or not that fallout rate would hinder production, this may be a potential interim solution. I have seen some of the top t-nuts strip out and not grab because the first 2 threads are gone.
Makes sense being that it is the same extrusion for both frame vertical and Y-Axis, thank you for making note of that. I believe the Y End plates are specified to the same thickness as TAZ 6 also, so definitely an issue with our double tapped extrusions on this delivery.
I checked some of the extrusions that we built the alpha units with and they had a minor diameter of 4.45 on average whereas the red tagged extrusions that we are seeing this issue with have a minor diameter of 4.75 on average so that explains it. I'll coordinate an inspection of the backstock and generate the NCMR. I will need to determine a threshold maximum minor diameter for these threads. @tutley @samantha do you have any recommendations? From the documents I've found, M5 x 0.8 threads should have a maximum of 4.33mm minor diameter, but I was thinking we could approve a variance up to 4.6mm without running into any issues.
@kent some of the M5 screws i measured the thread diameter of are around 4.85 on the low end, and 4.93 on the high end.
so i personally think 4.6 may be to high, as it doesnt leave much thread engagement across the range of screw diameters.
i can try and drill some holes to various sizes in a block of aluminum and then tap them and we can do a pullout and or strip out test to determine what will be the best range for us
I took a random sample of 40 extrusions from the pallet on the dock and measured the minor diameters with a pin gauge. Here are the results:
I think the parts in the new PO are going to work fine. It looks like if anything it's just a WIP issue.